Webbing Take-Up Device Acceleration Sensor Inversion
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing webbing take-up devices for vehicle seatbelts face challenges in reducing the size of acceleration sensors while maintaining their operational effectiveness, particularly when the vehicle decelerates sharply and the device tilts due to reclining mechanisms.
Innovation Solution
A webbing take-up device design where the acceleration sensor's housing is rotatable with its center of gravity positioned below the rotating axis, allowing it to maintain attitude during tilting, and featuring a spherical inertial mass body that rolls to operate the lock mechanism, eliminating the need for additional weights and simplifying the structure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If a weight portion is added at the lower side of the inertial body to lower the center of gravity, then the acceleration sensor can maintain its attitude during tilting, but the size of the acceleration sensor increases
Solution Approach 1:
Instead of adding weight at the lower side to lower the center of gravity, the patent inverts the approach by positioning the rotating axis above the center of gravity. This creates a pendulum-like effect where the housing naturally maintains its attitude during tilting through the gravitational torque on the inertial body, eliminating the need for additional weight portions and reducing overall sensor size.
2Volume of moving object
If the center of gravity of the housing is positioned at the upper side with respect to the rotating axis, then the size of the acceleration sensor is reduced, but the attitude maintenance capability during tilting is compromised
Solution Approach 1:
The patent employs dynamic attitude maintenance through the rotatable housing and pendulum mechanism. The housing can rotate about the horizontal axis, and the inertial body's position relative to the rotating axis creates a dynamic balance that automatically maintains the sensor's attitude during vehicle tilting, rather than relying on static weight distribution.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This design reduces the size of the acceleration sensor, maintains its operational effectiveness during vehicle deceleration and tilting, and operates the lock mechanism efficiently to restrain occupants, while avoiding the need for additional weights and complex shapes.
Implementation Method 1
an inertial mass body placed in the housing of the acceleration sensor moves by inertia
Implementation Method 2
the spherical body rolls on the curved surface by inertia and rises up the curved surface
Data Source
Figure 1
Figure 2
Figure 3
AI summary
An acceleration sensor of a webbing take-up device is provided with a sensor housing in which a spherical body is placed. A rotating shaft is formed at a longitudinal wall of a support wall of the sensor housing, and rotatably supported at a shaft receiving hole formed in a hanger support wall. A position of formation of the rotating shaft is set to be upward relative to a center of gravity of the sensor housing whose state where a sensor lever is installed at the support wall and the spherical body is placed on a curved-surface of a placing portion. Consequently, even without a heavy body being attached at the lower side of the spherical body or the lower side of the sensor housing, the sensor housing rotates responsively when the take-up device main body is tilted. Therefore, the acceleration sensor can be reduced in size.